1. Field of the Invention
The present invention relates to insulation for vehicles, and especially to thermal and sound insulation installed within vehicles such as aircraft, trains, boats, automobiles and trucks.
2. Description of Related Art
The demand for faster and more comfortable vehicles has resulted in many problems for vehicles designers. One such problem is that thermal and acoustical insulation must be carefully selected to make sure that the vehicles remain comfortable and relatively quiet under a wide range of environmental demands. These demands are particularly stringent in the design of aircraft which regularly undergo dramatic temperature changes and which must screen intense operational noise.
Although not as extreme, other vehicles may also require considerable air-conditioning and acoustical insulation in order to comply with the demands of travelers or shippers. This is a growing concern in a variety of vehicles, such as high-speed trains, automobiles and trucks, and watercraft.
Another constraint placed upon vehicles today is that faster vehicles generally require better sealing of seams and portals so as to minimize noise, maintain pressure differentials, and improve laminar flow around the shell of the vehicle. Unfortunately, since tightly sealed vehicle shells do not freely exchange air with the outside of the vehicle, heavy demands are placed upon the ability of air-conditioning systems to vent moisture out of the vehicles.
Very tightly sealed vehicles, such as high-speed jet aircraft, can experience extensive moisture build-up in the passenger cabin from breath, perspiration, steam from foods, etc. When the exterior of such vehicles are at a lower temperature than the interior and/or undergo substantial changes in temperature, the moisture vapor in the interior air tends to condense against the shell or within insulation surrounding the shell.
The build-up of moisture within insulation surrounding a vehicle's shell is a multi-faceted problem. First, many insulation materials commonly used today, such as fiberglass and certain foams, have a tendency to retain water once wetted. As a result, the insulation increases in its weight over time as condensate forms and remains within the insulation. In vehicles where increase in weight can result in substantial differences in fuel costs (e.g. aircraft), this build-up of moisture results in lo astronomical waste in fuel. With the steadily increasing costs of fuels, weight is further becoming a concern in virtually all forms of vehicles, including automobiles, trucks, trains, and watercraft.
Second, the build-up and retention of water also poses a number of safety and health hazards. For example, the accumulation of water: (a) contributes to a corrosive environment on the concealed interior of the vehicle's shell and, if left unchecked, can weaken important structural parts; (b) reduces the maneuverability of the vehicle through excessive weight gain; and (c) promotes an unsanitary environment where microorganisms can grow.
Third, the presence of moisture in certain insulations will tend to distort or decay the insulation over time. This occurs due to the increased weight of wet insulation in sidewalls which draws the insulation downward. Eventually gaps will develop which reduce both the thermal and acoustical insulative properties of the insulation. Water will also decay certain insulations which can further reduce their insulative properties.
Fourth, eventually insulation will become saturated with moisture which can result in the dripping of condensate into the cabin or a sizable accumulation of water along the bottom of the vehicle's shell.
Earlier insulations employed in aircraft and similar vehicles were simply loose fibers or batts packed between the shell of the vehicle and the interior walls. Among the deficiencies of this insulation system was that it tends to be hard to install and maintain, and the insulation tends to slide out of position.
More recently in the aircraft industry it has been recognized that the insulation should be regularly removed so that the interior of the fuselage can be inspected for corrosion and other problems. To accomplish this, a number of companies have begun wrapping insulation into insulation packages which can be easily removed and reinstalled. Unfortunately, by placing the insulation within a casing material, the insulation package decreases the flow of air through the insulation and increases the retention of water.
One proposed solution to this problem has been to wrap the insulation within a casing of MYLAR.RTM. polyester film or other impermeable membrane which will be resistant to liquid and moisture vapor penetration. However, in order to compensate for pressure changes, some breathing holes have been required in the polyester material. These pressure compensation holes have resulted in inevitable ingress of moisture vapor and water build-up. Moreover, the fact that the casing material is essentially liquid and vapor impermeable means that, once the insulation becomes damp, the insulation package remains wet for a very long period of time.
Accordingly, it is a primary purpose of the present invention to provide an insulation system for vehicles which limits moisture retention and the problems inherent with such retention.
It is another purpose of the present invention to provide a vehicle insulation system employing a wrapped insulation package which can be readily installed and maintained but which does not contribute to increased moisture retention.
It is a further purpose of the present invention to provide a vehicle insulation system which contains liquid water away from the vehicle's shell while permitting the evaporation of water from the insulation material.
These and other purposes of the present invention will become evident from review of the following specification.